METHOD AND APPARATUS FOR REMOVING CONDENSATE FROM COMBUSTION ANALYZER SAMPLE

PROCEDE ET APPAREIL D'EXTRACTION DES CONDENSATS D'ECHANTILLONS POUR ANALYSEURS DE COMBUSTION

English Abstract

A trap for removing moisture from sampled gases containing moisture in vapor
and/or entrained liquid form includes an elongate conduit (4) having a plug
(2) substantially centrally positioned therein to prevent flow directly
through the conduit (4), the conduit (4) being provided with a radially
directed hole (6-7) on each side of the plug (2). A tube (1) is substantially
concentric with the conduit (4) and has stoppers (3) at opposite ends thereof
with openings therein for the conduit (4) to pass therethrough. At least one
of the stoppers (3) is provided with a second opening (5) which can be stopped
during sampling and unstopped for draining. During sampling, sample gases are
drawn into one end of the conduit (4) and exhausted radially into the space
between the conduit (4) and the tube (1) such that vapor condenses on the
inner surface of the tube (1), entrained liquid collects on the inner surface
and the gas enters the conduit (4) on the other side of the plug (2) and
exhausts to an analyzer.

French Abstract

L'invention porte sur un piège servant à extraire d'un échantillon de gaz l'humidité présente sous forme de vapeur et/ou de liquide entraîné, et consistant en un conduit allongé (4) comportant sensiblement en son centre un bouchon (2) empêchant le passage direct du flux dans le conduit (4), lequel est percé d'un trou radial (6, 7) de chaque côté du bouchon (2). Un tube (1) sensiblement concentrique au conduit (4) est muni à ses extrémités opposés d'obturateurs (3) percés d'ouvertures livrant passage au conduit (4). L'un au moins des obturateurs (3) est percé d'un deuxième orifice (5) pouvant être fermé pendant l'échantillonnage et ouvert pendant la vidange. Pendant l'échantillonnage, les échantillons de gaz entrent par l'une des extrémités du conduit (4) puis passent radialement dans l'espace compris entre le conduit (4) et le tube (1), de manière à ce que la vapeur d'eau se condense sur la surface intérieure du tube (1), que le liquide entraîné soit recueilli sur la surface intérieure et que le gaz pénètre dans le conduit (4) de l'autre côté du bouchon (2) et sorte en direction de l'analyseur.

Claims

I CLAIM:
1. A trap for removing moisture from sampled
gases containing moisture in vapor and/or entrained liquid
form comprising:
a) an elongate conduit having a plug
substantially centrally positioned therein to prevent flow
directly through the conduit, said conduit being provided
with a radially directed hole on each side of the plug
adjacent thereto; and
b) a tube being substantially concentric with
said conduit and having stoppers at opposite ends thereof
with openings therein for the conduit to pass therethrough,
at least one of the stoppers being provided with a second
opening which can be stopped during sampling and unstopped
for draining,
whereby, during sampling, sample gases are drawn
into one end of said conduit and exhausted radially into the
space between the conduit and the tube such that vapor
condenses on the inner surface of the tube, entrained liquid
collects on the inner surface and the gas enters the conduit
on the other side of the plug and exhausts to an analyzer.
2. A trap as set forth in claim 1 wherein the
conduit is tubular and the tube is cylindrical.
3. A trap as set forth in claim 2 wherein the
conduit is of small diameter relative to the diameter of the
tube.
4. A trap as set forth in claim 1 wherein the
radially directed holes in the elongate conduit are
positioned 130° to each other.
5. A trap as set forth in claim 1 wherein the
conduit is stainless steel, the tube is clear polycarbonate
and the plug and stoppers are rubber.
- 5 -

6 A trap as set forth in claim 5 wherein the
tube is 1" in diameter and includes an axial space of about
31/2" between stoppers.
7. A method for removing moisture from sampled
gases containing moisture in vapor and/or entrained liquid
form comprising the steps of:
a) drawing gases to be sampled into one end of
an elongate conduit having a plug approximately midway in
its length;
b) exhausting the gases radially through a hole
in the conduit on one side of the plug into a space between
the conduit and a larger tube;
c) maintaining the larger tube at a temperature
below the dew point of the sampled gases such that vapor
condenses on an inner surface of the tube and entrained
liquid collects on the inner surface;
d) redrawing the gases from the space between
the conduit and the larger tube radially through a hole in
the conduit on the opposite side of the plug into the
conduit; and
e) exhausting the gases to the analyzer for
analysis.
- 6 -

Description

- CA 02240423 1998-06-12
WO 97/26067 PCT~US97~00840
MET~OD AN~ APPARATUS FO~ REMOVING CONDENSATE
FROM COMBUSTION ANALYZE~ SAMPLE
FIELD OF THE lNv~NllON
This invention pertains to the field of gas
analysis, particularly, flue gas analysis and,
specifically, to removal of moisture from the sample gases
prior to analysis.
BACKGROUND OF THE lNVl~;N'l'lON
In order to analyze flue gases, for example, it
is nPcP~ary to draw moisture laden gases into the sampling
system. The moisture may be in the form of vapors or
entrained liquid. The moisture in the gases, when it
condenses, damages pumps and sensors interfering with the
analysis. Since the analysis may be made at the location
of a home furnace by furnace repairmen that carry all
equipment to the location of testing, there exists the need
for a simple, rugged piece of equipment for removing
moisture from flue gases prior to analysis.
An example of a gas sampling device is disclosed
in U.S. Patent No. 5,018,395 entitled "Gas Sampling Device
With T _- vved Mixed Flow Fan" assigned to the same assignee
as this application.
Present solutions to the moisture problem are not
satisfactory. One solution replaces a reciprocating pump
25 with a mixed flow or centrifugal fan which can pass the
con~Pn~te, however, this does not solve the problem of the
moisture in the analyzer. Moreover, the suction that can
be drawn by a centrifugal fan is typically limited to a 1
inch water column. Another solution is to pass the sample
30 through a desiccant. The desiccant needs to be replaced
hourly in currently used volumes, say, a liter per minute.
The desiccant must then be reactivated by heating in an
oven.
A complicated apparatus for condensing moisture
* 35 from flue gas prior to analysis is disclosed in U.S. Patent

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W O 97/26067 PCTrUS97/00840
No. 3,680,388. Another apparatus for ?chAn;cally removing
moisture from flue gases is disclosed in U.S. Patent No.
5,240,486. In the latter device, flue gas is drawn in a
tube and axially exhausted against a plate and then drawn
into yet a larger volume before being exhausted to the
analyzer.
It is an advantage of the moisture trap,
according to this invention, that it is extremely simple to
manufacture and use. The trap can be positioned in any
orientation and still effectively trap moisture. Moreover,
it is easily and quickly drained and returned to service.
Briefly, according to this invention, there is
provided a moisture trap for removing moisture from sampled
gases containing moisture in vapor and/or entrained liquid
form. The trap comprises a small diameter elongate tubular
conduit having a plug centrally positioned therein to
prevent flow directly through the conduit. The conduit is
provided with two radially directed holes, one positioned
on each side of the plug and adjacent thereto, say, within
~ inch. A large diameter tube substantially concentric
with the elongate tubular conduit is secured in place by
plugs at each end thereof with openings therein for the
elongate tubular conduit to pass therethrough. At least
one of the plugs is provided with a second passage
therethrough that can be stopped during sampling and
unstopped for draining. The plug in the elongate tubular
conduit is positioned to be approximately halfway between
the plugs in the ends of the large diameter tube. Thus,
during sampling, sample gases are drawn into one end of the
elongate tubular conduit, exhausted radially into the space
between the conduit and the tube such that vapor condenses
on the inner surface of the tube and entrained liquid
collects on the inner surface. The gas then re-enters the
conduit on the other side of the plug and exhausts to the
analyzer. ~egardless of the orientation of the trap, it
-- 2

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WO 97/26067 PCTnUS97~0~84a
can accumulate li~uid up to about 40% o~ its volume prior
to requiring draining. Preferably, the radial holes in the
elongate tubular conduit are positioned 180 opposite to
each other.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and other objects and advantages
will become clear from the following detailed description
made with reference to the drawings in which:
Fig. l is a side view of a moisture trap
according to this invention; and
Fig. 2 is a section view through a moisture trap
according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figs. 1 and 2, a large diameter
tube 1 which may, for example, comprise a 1 inch tube of
clear polycarbonate, is provided with end stoppers or plugs
made of rubber 3. The rubber end stoppers have an axially
or centrally positioned passage therethrough for receiving
a stainless steel tubing. The stainless steel tubing has
a rubber plug 2 positioned therein. On each side of the
plug and adjacent thereto are radial openings through the
wall of the stainless steel tubing 6 and 7. At least one
of the end plugs is provided with a passage 5 into which a
drain plug or valve may be inserted.
The sample gas (and condensate formed during the
passage of the sample from the flue to the trap) enters the
stainless steel tubing 4 from either end. It is
interrupted by the plug 2 and exits radially to the space
between the stainless steel tubing and the large diameter
tube to cool further and to trap the condensate. The cool
saturated sample re-enters the stainless steel tubing on
the opposite side of the plug and flows out to the analyzer
pump through the tubing.
The above-described apparatus has been tested in
the laboratory. The trap had a 1 inch diameter tube with

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W O 97/26~67 PCTAUS97/0084
an axial space of about 3~ inches between plugs. Flue
gases having a dew point of 130 and at a temperature of
about 400 to 600 F were passed through the trap. In
about 80 minutes, approximately 40% of the volume of the
trap was filled with li~uid. The li~uid could be drained
from the trap by removal of the plug within about 15
seconds.
It is not essential that the tubing and large
diameter tube be cylindrical in cross section. Other cross
sections are suitable. The size of the larger tube can
vary. It is important that the inner surface of the tube
have an ade~uate area for transmitting heat outwardly. The
materials from which the tube and tubing are fabricated are
not critical. The stoppers and plug in the tubing may be
rubber or any other elastomeric material that will be
resilient at temperatures encountered.
Having described presently preferred embodiments
of the invention, it is to be understood that it may be
otherwise ~- ho~; ed within the scope of the appen~led claims.

Representative Drawing